Sodium tests of head-flow characteristics for prototype annular electromagnetic flow coupler.

Abstract

A prototype annular electromagnetic flow coupler was tested with high temperature sodium and it worked successfully, verifying the operational principle. The pump head-flow characteristics of the coupler were first clarified from an analysis of its equivalent electric circuit. The pump head and the generator pressure drop decrease linearly with the pump flow rate under the conditions of constant generator flow rate and external magnetic flux density. The gradients of the linear changes are given by ratios of equivalent resistances in the electrical analog, and are independent of the generator flow rate, if the magnetic flux density is kept constant. Sodium tests of the prototype confirmed the above results when the Hartmann number of the test conditions is larger than 170. Both ratios of the differential pressures and the volumetric flow rate between pump and generator ducts exceed 50% while the wall loss of around 40% appears at peak efficiency due to the lack of electrical insulation and the relatively large wall thickness. The peak efficiency of the prototype coupler decreases with the sodium temperature at the rate of (2.33±0.21)x10−2 %/°C from 200 to 400°C and increases with the external magnetic flux density at 5.8±0.1 %/T from 0.36 to 0.60T.